Alternator wiring question

[conchy joe]

I think I have a Delco style alternator and I am having a fit trying to figure out which wires go where. I know the the BAT wire is for the battery, but there are two spades on the side of the case and a second post with a nut and of course the ground bolt.

If my thinking is correct I need to hook up the yellow wire with red tracer, the grey tach wire, but there are three empty terminals. I'm guessing the yellow with the red tracer goes to the #2 spade terminal and the grey wire goes to the #1 spade terminal, but what the heck goes on the second smaller post???

Thanks guys